Cardiac arrhythmia is term used to broadly describe a group of cardiac conditions involving abnormal electrical activity in the heart. In atrial fibrillation (AF), the most common type of cardiac arrhythmia, disorganized electrical impulses (usually generated by the roots of the pulmonary veins) interrupt the normal electrical impulses generated by the sinoatrial node, which in turn causes an irregular conduction of electrical impulses to the heartbeat-generating ventricles. AF may result from a number of conditions, such as hypertension, coronary artery disease, pericarditis, lung disease, hyperthyroidism, carbon monoxide poisoning, or rheumatoid arthritis.
Catheter ablation frequently used to treat AF, which involves a minimally invasive procedure by which areas of cardiac tissue that facilitate the irregular electrical conduction are ablated using any of a number of energy modalities. During catheter ablation, one or more pulmonary veins (PVs) may be targeted. AF is commonly initiated by foci located in the PVs. PVs are large blood vessels that carry oxygenated blood from the lungs to the left atrium (LA) of the heart. In order to disrupt the propagation of abnormal electrical currents, the ablation catheter is placed around the opening of the PV to the heart and/or within the PV where the foci are located. However, the PVs are usually not regularly shaped, and often have an asymmetrical interior that can be difficult to navigate. Further, the openings of two closely positioned PVs may form a single irregular opening, which can make ablation with many currently used ablation elements ineffective (for example, single loop-style ablation elements or the treatment elements of focal catheters). Additionally, the treatment of other types of cardiac arrhythmia may require ablation of tissue in or around the PV and tissue in other areas of the heart. However, it is often necessary to use more than one device in order to effectively destroy aberrant electrical currents. Having to replace a device during surgery can be time consuming, difficult to accomplish, and potentially dangerous for the patient.
Currently available devices may be used to treat conditions such as complex fractionated arterial electrograms (CFAEs), used for septal ablation, used to ablate pulmonary vein ostia, and used to create linear ablation lesions. Each of these devices is effective in ablating tissue, and each may be particularly suited to a certain area of anatomy. For example, some catheters may includes an electrode array that is well-suited for creating circumferential lesions about pulmonary vein ostia, whereas others do not include an expandable treatment element and are effective in creating linear lesions. As such, it may be necessary to use multiple ablation devices for treating a single atrial fibrillation patient, depending on the location(s) and number of aberrant electrical pathways that must be addressed.
Accordingly, an ablation device having one or more ablation elements suitable for treating aberrant electrical currents in a variety of cardiac locations is desired. In particular, the desired device is suitable for treating AF and other arrhythmias by ablating a variety of cardiac tissues, including the pulmonary veins, septum, and heart wall.